Tiny flashes of infrared light can play a role in healing wounds, building muscle, turning back the worst effects of diabetes and repairing blinded eyes -- on this much, scientists and doctors agree. But what they can't decide on is why all these seemingly miraculous effects happen in the first place.For more than a decade, researchers have been studying how light-emitting diodes, or LEDs -- miniscule, ultra-efficient bulbs like the ones found in digital clocks and television remotes -- might aid in the recuperative process. NASA, the Pentagon and dozens of hospitals have participated in clinical trials. Businesses have sold commercial LED zappers to nursing homes and doctors' offices. Magazines and television crews have drooled on cue. Medicare has even approved some LED therapy.Despite all that effort, "there's not a clear idea of how this works. There are just working hypotheses," said Marti Jett, chief of the molecular pathology department at the Walter Reed Army Institute of Research.One possibility comes from Dr. Harry Whelan, a colleague of Jett's and a neurology professor at the Medical College of Wisconsin. In a 2002 study backed by the National Institutes of Health and the Persistence in Combat program from the Pentagon's research arm, Whelan used LEDs to restore the vision of blinded rats. Toxic doses of methanol damaged the rats' retinas. But after exposure to the flashes of infrared light, up to 95 percent of the injuries were repaired.Human trials have been less dramatic, but still shockingly effective. Using a Food and Drug Administration-approved, handheld LED -- playfully called Warp 10 for its Star Trek style -- wound-healing time was cut in half on board the USS Salt Lake City, a nuclear sub. Diode flashes improved healing of Navy SEALs' training injuries by more than 40 percent. And a Warp 10 prototype was used by U.S. Special Forces units in Iraq, Whelan asserts.These LEDs originally were developed by NASA to stimulate plant growth. Now, the agency wants to use the gadgets to build astronauts' muscles during weightlessness. DNA synthesis in muscle cells quintupled after a single application of LEDs flashing at the 680-, 730- and 880-nanometer wavelengths, according to Whelan.How exactly all this happened remains a mystery, Jett said. She's identified more than 20 genes that typically are associated with retinal damage, for example, and "the LED alters all of them."My Wired News story has more on the puzzling power of LEDs.

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